Ni-Catalyzed Enantioconvergent\nKumada–Corriu\nCross-Coupling between β‑Bromostyrenes and Secondary\nGrignard Reagents: Reaction Development, Scope and Mechanistic Investigations

A Ni-catalyzed enantioconvergent cross-coupling between\nβ-bromostyrenes\nand secondary Grignard reagents is reported. This C(sp<sup>2</sup>)–C(sp<sup>3</sup>) cross-coupling is applicable to a broad\nrange of electrophilic and nucleophilic partners and affords the products\nin good to high levels of enantio-induction. Experimental mechanistic\ninvestigations revealed an unexpected binding mode of the chiral (P,N)\nligand and support a radical rebound mechanism involving in-cage radicals.\nKinetic experiments provide evidence for an off-cycle resting state\nfeaturing\ndinuclear species. Computational analyses are in line with this hypothesis\nand coherent with a catalytic cycle proceeding via a Ni(I)/Ni(III)\nmanifold. They further suggest an enantio-determining radical capture\nevent and shed light on the origin of the Dynamic Kinetic Resolution\nprocess.